Accelerated weight drop for use as a seismic energy source and a method of operation thereof

ABSTRACT

The present invention provides an accelerated weight drop for use as a seismic energy source, a method for operating an accelerated weight drop for use as a seismic energy source, and a seismic survey system including the accelerated weight drop. The accelerated weight drop, among other elements, may include a striker positionable over a surface, a compressed gas spring configured to drive the striker toward the surface thus creating seismic waves within the surface, and a cushioning means positioned proximate the compressed gas spring for dissipating reflected energy. In this embodiment the striker is slidably coupled to the compressed gas spring.

TECHNICAL FIELD OF THE INVENTION

The present invention is directed, in general, to a seismic energysource and, more specifically, to an accelerated weight drop for use asa seismic energy source, a method of manufacture therefor, and a seismicsurvey system including the accelerated weight drop.

BACKGROUND OF THE INVENTION

Seismic geophysical surveys are used in petroleum, gas mineral and waterexploration to map the following: stratigraphy of subterraneanformations, lateral continuity of geologic layers, locations of buriedpaleochannels, positions of faults in sedimentary layers, basementtopography, and others. Such maps are deduced through analysis of thenature of reflections and refractions of generated seismic waves frominterfaces between layers within the subterranean formation.

A seismic energy source is used to generate seismic waves that travelthrough the earth and are then reflected by various subterraneanformations to the earth's surface. As the seismic waves reach thesurface, they are detected by an array of seismic detection devices,known as geophones, which transduce waves that are detected intorepresentative electrical signals. The electrical signals generated bysuch an array are collected and analyzed to permit deduction of thenature of the subterranean formations at a given site.

Seismic energy sources that have been used in geophysical survey methodsfor petroleum, gas, copper, coal, diamond and other mining explorationoperations include explosives, vibratory sources and impact sources. Thenature of output seismic energy depends on the type of seismic energysource that was used to generate it.

Explosive seismic energy sources used in petroleum and gas explorationon land rely on the explosion of material placed within a subterraneanformation to generate seismic waves. Typically, a hole is drilled in theground, the explosive is placed in the hole, and backfill is piled ontop of the explosive, prior to initiating the explosion. Compared on apound for pound basis to other energy sources, explosive sources imparta very high amount of seismic energy into the ground. Explosive seismicenergy sources currently being used in geophysical survey methodsgenerally produce waves of very high frequency.

Many explosives used in seismic energy sources generate high gasvolumes. This is a useful property in mining for moving rock, but isundesirable in seismic exploration, because it decreases the amount ofusable seismic energy that is generated. Explosives that produce highvolumes of gas cause much of the energy of the explosion to be lost asexpanding gases force backfilled material up the borehole into which theexplosive was placed. Thus, less of the energy generated by theexplosion is transferred into the subterranean formation than would betheoretically possible if less energy was lost to the expansion ofgenerated gases. Further, as the explosives are considered bombs incertain countries, their use is severely limited.

Vibratory sources are also used as seismic energy sources in geophysicalsurvey methods. Two categories of vibratory sources include those thatgenerate seismic waves originating at the surface and those thatgenerate seismic waves that emanate from downhole. Onemechanical-hydraulic vibratory source, the Vibroseis truck, is speciallydesigned to place all of its weight onto a large platform whichvibrates. This vibration, in turn, produces seismic waves in thesubterranean formation. Vibroseis trucks have been used extensively ingeophysical survey methods, not just for the petroleum and gasexploration, but also for studying the evolution and development ofspecific geological structures (e.g., the Rocky Mountains) and faultlines. Vibratory sources tend to produce highly repeatable seismicenergy. The nature of the energy delivered into the ground by vibratorysources, its amount, duration, and time of delivery, can be tightlycontrolled and therefore the seismic energy generated tends to be veryreproducible, which is a benefit. However, vibratory sources are oftennot suited to certain types of terrain. For example if the ground isvery soft, it can be difficult to use Vibroseis trucks as a seismicenergy source.

Fundamentally, an impact source is a weight striking the surface of theearth directly or impacting a plate placed on the earth's surface,yielding seismic energy. A weight-drop is an example of the former typeof impact source. Impact sources tend to be relatively inexpensive, andsimple to operate and maintain. Additionally, they do not bring aboutmany of the disadvantages associated with the former two impact sources.Unfortunately, their principal disadvantage is that they are inefficientat continuously producing seismic energy useful for geophysical surveyof deeper layers. Impact sources typically tend to yield a relativelyhigh proportion of low frequency, surface waves and output less seismicenergy than other seismic energy sources.

Accordingly, there is a need in the art for improved seismic methods andgeophysical survey systems that rely on impact sources that convert ahigher amount of the potential energy in the impact source into seismicenergy.

SUMMARY OF THE INVENTION

To address the above-discussed deficiencies of the prior art, thepresent invention provides an accelerated weight drop for use as aseismic energy source, a method for operating an accelerated weight dropfor use as a seismic energy source, and a seismic survey systemincluding the accelerated weight drop. The accelerated weight drop,among other elements, includes a striker positionable over a surface, acompressed gas spring configured to drive the striker toward the surfacethus creating seismic waves within the surface, and a cushioning meanspositioned proximate the compressed gas spring for dissipating reflectedenergy. In this embodiment the striker is slidably coupled to thecompressed gas spring.

As indicated above, the present invention further provides a method foroperating an accelerated weight drop for use as a seismic energy source.The method for operating the accelerated weight drop includespositioning a striker over a surface, the striker slidably coupled to acompressed gas spring having a cushioning means positioned proximatethereto, and driving the striker toward the surface using the compressedgas spring to create seismic waves within the surface, wherein thecushioning means is configured to dissipate reflected energy.

The present invention further provides a seismic survey system. Withoutbeing limited to such, the seismic survey system includes: 1) anaccelerated weight drop, as described above, 2) at least one geophoneplaced proximate the surface, wherein the geophone is configured tocollect information from the seismic waves, and 3) a seismic recorderconnected to the at least one geophone, the seismic recorder configuredto record the collected information.

The foregoing has outlined preferred and alternative features of thepresent invention so that those skilled in the art may better understandthe detailed description of the invention that follows. Additionalfeatures of the invention will be described hereinafter that form thesubject of the claims of the invention. Those skilled in the art shouldappreciate that they can readily use the disclosed conception andspecific embodiment as a basis for designing or modifying otherstructures for carrying out the same purposes of the present invention.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates a cross-sectional view of one embodiment of anaccelerated weight drop for use as a seismic energy source constructedin accordance with the principles of the present invention;

FIGS. 2-5 illustrate simple schematic cross-sectional views illustratinghow one might operate an accelerated weight drop manufactured inaccordance with the principles of the present invention as a seismicenergy source; and

FIG. 6 illustrates a seismic survey system constructed in accordancewith the principles of the present invention.

DETAILED DESCRIPTION

Referring initially to FIG. 1 illustrated is a cross-sectional view ofone embodiment of an accelerated weight drop 100 for use as a seismicenergy source constructed in accordance with the principles of thepresent invention. The accelerated weight drop 100 illustrated in FIG. 1includes a striker 120 positionable over a surface 110. The surface 110,as one skilled in the in the art of seismic geophysical surveys couldimagine, might comprise a number of different surfaces while stayingwithin the scope of the present invention. For example, the surface 110may comprise soil itself, or in another embodiment might comprise arigid surface coupled to the soil, such as a cement footing or anothersimilar rigid surface. The rigid surface might be beneficial in loosesoil conditions, such as sand, as might be found in petroleum or gasfields throughout the United States or world. Similarly, the surface 110may comprise both horizontal and vertical surfaces, as well as anythingin-between.

The striker 120, which may consist of a hammer like design, is typicallya very heavy structure. For example, in one embodiment of the inventionthe striker has a weight that ranges from about 1000 pounds to about2500 pounds. This weight, however, may easily be changed or tailored tomeet a specific purpose. For instance, where a surface 110 needs alarger seismic energy source than might be provided using theabove-referenced 1000 pound to 2500 pound striker 120, the weight of thestriker 120 could be increased to accommodate the desired, largerseismic energy source. Similarly, a smaller and more mobile striker 120could be used in an accelerated weight drop 100 that is configured to becarried and used in a mining shaft by individuals. In such acircumstance a striker 120 weighing between about 25 pounds and about100 pounds could be used. Given the multiple number of uses for theaccelerated weight drop 100, the present invention should not be limitedto any specific striker 120 weight.

The striker 120, in the embodiment shown in FIG. 1, comprises aneight-inch diameter cylindrical piece of hardened steel. The diameter,as well as the geometric configuration and the material chosen to formthe striker 120, however, could be changed to accommodate the variousweights discussed above. In the illustrated embodiment, the striker 120has a substantially flat surface. This allows the striker 120 to easilytransfer its impact load to a contacted surface.

The striker 120, through the use of a push rod 130, is slidably coupledto a compressed gas spring 140. While the embodiment shown in FIG. 1exhibits the striker 120 slidably connected to a single compressed gasspring 140, it is foreseeable that multiple compressed gas springs beslidably coupled to the striker 120 through push rod 130. The push rod130 may be any structure capable of connecting the striker 120 to thecompressed gas spring 140, and stay within the scope of the presentinvention. Nonetheless, in the embodiment shown in FIG. 1 the push rod130 comprise a 2-3 inch diameter steel rod having a material strengthsufficient to handle any forces transferred to or from the striker 120.

The compressed gas spring 140, which is configured to drive the striker120 toward the surface 110, includes a gas chamber 143 and a piston 148.As is illustrated, the piston 148 is configured to slide within the gaschamber 143 to create a pressure therein. This pressure, in turn, willuniquely be used to assist the drive of the striker 120 toward thesurface 110 at a high rate of speed.

Both the gas chamber 143 and the piston 148 may comprise conventionalmaterials for their manufacture. As an example, most of the materialsused to manufacture the accelerated weight drop 100 could be purchasedat any standard steel yard, and if required, could be assembled andtailored where needed by any skilled machinist, given the teachingsherein. The gas chamber 143 in the embodiment of FIG. 1 comprises athree-inch diameter bulk pipe having a length of about 29 inches, and anupper surface closed to the atmosphere.

Optionally coupled to the gas chamber 143 is a charging port 150. Thecharging port 150, which might be a standard air chuck similar to thatused on an automobile tire, is configured to charge the gas chamber 143before, during or after using the accelerated weight drop 100. In anexemplary embodiment, the charging port 150 is used to add nitrogen gasto the gas chamber 143. While any known or hereafter discoveredcompressible gas could be used to create the pressure within the gaschamber 143, nitrogen gas is very useful as it does not contain themoisture and particulate matter commonly contained within atmosphericair. Additionally, nitrogen is safe to handle and relatively inexpensiveto use.

Also, optionally coupled to the gas chamber 143 in the embodiment ofFIG. 1 is a pressure gauge 155. As one skilled in the art would expect,the pressure gauge 155 may be used to observe a pressure within the gaschamber 143 before, during or after use of the accelerated weight drop100. Given this pressure, a calculation means could be used to calculatean impact load that might be placed upon the surface 110 by the striker120.

Partially surrounding the striker 120, and in the embodiment illustratedand discussed with respect to FIG. 1 surrounding the compressed gasspring 140, is a housing 160. The housing 160, in the disclosedembodiment, includes a main portion 160 a and a secondary portion 160 b.The main portion 160 a acts as a manifold or guide for the striker 120.In the advantageous embodiment shown and discussed with respect to FIG.1, the main portion 160 a consists of a conventional 10 inch diameter 6foot long piece of bulk pipe at least partially surrounding the striker120. The main portion 160 a may further include a 12 inch by ⅜ inchchannel iron that is approximately 6 foot long coupled to the bulk pipe.This channel iron allows other devices, such as a hydraulic press 163for transferring a static load to the housing 160 or a hydraulic lift165 for lifting the striker 120 into a cocked position, to be rigidly orremovable coupled thereto.

In contrast, the secondary portion 160 b extends up and at leastpartially around the gas chamber 143. In this instance, the secondaryportion 160 b comprises a five-inch diameter bulk pipe sheathing coupledto the first portion 160 a and surrounding the gas chamber 143.Additionally, welded to the top surface of the sheathing may be a ½ inchthick 5¼ inch diameter cap.

Uniquely positioned proximate the compressed gas spring 140 are one ormore cushioning means 168. The cushioning means 168, which may comprisea number of different structures without departing from the principlesof the present invention, are configured to dissipate reflected energythat might arise during the operation of the accelerated weight drop100. In the embodiment shown, two cushioning means 168 a and 168 b areused. As is advantageously illustrated, cushioning means 168 a ispositioned between the push rod 130 and the striker 120. As is alsoadvantageously illustrated, cushioning means 168 b is positioned betweenthe gas chamber 143 and the secondary portion 160 b of the housing 160.

While the cushioning means 168 are advantageously illustrated as rubbergaskets in the embodiment illustrated and discussed with respect toFIGS. 1-6, those skilled in the art understand that other structures ormaterials would suffice. For example, it can be envisioned where therubber gaskets are exchanged for foam or another absorptive material.Similarly, it can be envisioned where a fluid absorptive bladder couldreplace one or more of the cushioning means 168.

In an exemplary embodiment of the invention, as shown, a strike plate170 may be positioned between the striker 120 and the surface 110.Specifically, the strike plate 170 in the embodiment of FIG. 1 ismovably coupled to the first portion 160 a of the housing 160. Thestrike plate 170, in this embodiment, is configured to transfer animpact load from the striker 120 to the surface 110, as well as accept astatic load from the housing 160. The interplay between the static loadand impact load will be discussed further below when discussing how theaccelerated weight drop 100 of FIG. 1 might operate.

The strike plate 170 may, in an advantageous embodiment, have an anvil173 coupled thereto. For example, a high integrity weld could be used torigidly couple the anvil 173 to the strike plate 170, or alternativelythe two structures could be bolted together. In another advantageousembodiment the strike plate 170 and the anvil 173 could comprise asingle structure, such as a structure formed in a single manufacturingprocess. Either of these configurations, or for that matter otherconfigurations not disclosed, are within the scope of the presentinvention.

Extending from a vertical surface of the anvil 173 are pins 178. Thepins 178 may either be welded to the anvil 173 or formed in the samemanufacturing process as the strike plate 170, anvil 173, or both thestrike plate 170 and the anvil 173. Similarly, the pins 178 could bebolted to the anvil 173. As will be shown below, the pins 173 are apoint of transfer of the static load from the housing 160 to the strikeplate 170.

An impact isolator 180 may be positioned between the housing 160 and thestrike plate 170, and more specifically between the housing 160 and thepins 178 connected to or forming a portion of the strike plate 170. Asis shown in the alternate view 183 of the accelerated weight drop 100,the impact isolator 180 may be rigidly coupled to the housing 160 andslidably coupled to the strike plate 170, or pins 178. For instance, inthe exemplary embodiment of FIG. 1 the impact isolator 180 comprises aplate 185 having a slot 188 located therein. As can be observed in FIG.1, the pins 178 are slidably coupled within the slot 188. The importanceof the impact isolator 180 will be discussed in detail during thediscussion of the method of operating the accelerated weight drop 100.

Uniquely included within the accelerated weight drop 100 is a catchmechanism 190. The catch mechanism 190, which in the embodiment of FIG.1 happens to be coupled to the housing 160, is designed to hold thestriker 120 in a cocked position. Among others, the catch mechanism 190may comprise a biased dog to hold the striker 120 in the cockedposition. The biased dog, such as a trip dog or slide dog, may beconfigured to cooperatively engage the striker. For instance, the slidedog shown in FIG. 1 is configured to cooperatively engage the notches125 in the striker 120. Again, it should be understood that themechanical catch 190 discussed herein is but one example and that onewho is skilled in the art would be able to arrive at other catchmechanisms, given the teachings of the present invention.

The accelerated weight drop 100 illustrated in FIG. 1 may contain otherfeatures that are also within the scope of the present invention. Forexample, one important feature of the present invention, which is notshown, is a safety mechanism that prevents the striker 120 from dryfiring. The striker 120, when in the transportation mode, should not befired. Therefore, the safety mechanism prevents the striker 120 fromfiring if the striker plate 170 is not located on the surface 110, and astatic load has not yet been placed on the striker plate 170.

Turning now to FIGS. 2-5 illustrated are simple schematiccross-sectional views illustrating how one might operate an acceleratedweight drop manufactured in accordance with the principles of thepresent invention as a seismic energy source. FIG. 2 illustrates anaccelerated weight drop 100 in a configuration that might be used forits transportation. For example, in the embodiment of FIG. 2, thehydraulic presses 163 are retracted causing the strike plate 170 to beheld a distance off of the surface 110. While it is shown that thestrike plate 170 is only held a small distance above the surface 110when the hydraulic presses 163 are completely retracted, this distancecan be increased by changing the throw distance of the hydraulic presses163. Similarly, devices other than the hydraulic presses 163 could beused to retract the housing 160 and strike plate 170 and stay within thescope of the present invention.

As is noticed in FIG. 2, the pins 178 slide to the lowest portion of theslot 188 when the hydraulic presses 163 are retracted. The pins 178,which are physically connected to the anvil 173 of the strike plate 170,are, therefore, the point at which the strike plate 170 is lifted. Thisunique feature eliminates the need to have to position the strike plate170 in place after the accelerated weight drop 100 reaches its desireddestination. As a result, the strike plate 170 is self-aligning beforeand after each set-up.

At this stage, the gas chamber 143 may or may not be charged with thedesired gas. Often, the gas chamber 143 always remains charged to someextent or another. In such an instance, the charging port 150 would onlybe used to recharge the gas chamber 143 after some or all of the gasundesirably escaped therefrom, to add additional gas into the chamberthereby increasing the impact load of the striker 120, or to evacuatethe gas chamber 143 to perform service thereon. The pressure gauge 155could be used to monitor the pressure within the gas chamber 143.

Optionally connected to the gas chamber 143 and a gas source may be agas monitoring and injection system. For example, a device capable ofmonitoring the pressure within the gas chamber 143 and maintaining apredetermined pressure within the gas chamber 143 could be used. Whenthe gas monitoring and injection system determines that the gas chamber143 deviates from the predetermined gas pressure, it injects gas intothe gas chamber 143 to restore it to the predetermined pressure. In thisinstance, the gas chamber 143 could always have the same predeterminedpressure, regardless of any small gas leaks that might be present.

Turning now to FIG. 3, illustrated is the accelerated weight drop 100illustrated in FIG. 2 after it has been positioned in a desired locationand the strike plate 170 placed upon the surface 110. This can beaccomplished by extending the hydraulic presses 163, thereby causing thestrike plate 170 to approach the surface 110. Further, not only does theextension of the hydraulic presses 163 cause the strike plate 170 toapproach the surface 110, the entire weight of the structure (e.g., astatic load) may be placed upon the strike plate 170 through the housing160 and the impact isolator 180. Note how the pins 178 are now locatedin an upper most portion of the slot 188 in the plate 185. This staticload, as will be discussed further below, helps transfer a substantialportion of the impact load directly to the surface 110.

Turning now to FIG. 4, illustrated is the accelerated weight drop 100 ofFIG. 3, after the striker 120 has been placed in a cocked position.Unique only to the present invention, the cocking of the striker 120causes the original volume of the gas chamber 143 to decreasesubstantially. But for the catch mechanism 190, the decreased volumewould tend to cause the striker 120 to drive toward the surface 110,thus creating seismic waves therein. Obviously, however, at this pointthe catch mechanism 190 would keep the striker 120 in the cockedposition.

Any sort of cocking means, such as the hydraulic lift 165 coupled to thestriker 120, could be used to lift the striker 120 to a cocked position.While the hydraulic lift 165 is illustrated in FIG. 4 as lifting thestriker 120, those skilled in the art understand that any known orhereafter discovered device capable of lifting the striker 120 to acocked position is also within the scope of the present invention. Forexample, the lifting mechanism might consist of cooperative ratchetgears or cable and pulley systems used to lift the striker to a cockedposition.

If desired, the gas chamber 143 may be further charged using thecharging port 150 after the striker 120 has been cocked. As one wouldexpect, the addition of the added gas within the gas chamber 143 wouldincrease the force the striker 120 is capable of delivering to thestrike plate 170.

Turning now to FIG. 5, illustrated is the accelerated weight drop 100illustrated in FIG. 4 after the catch mechanism 190 has been triggeredand the striker 120 is contacting the striker plate 170. Morespecifically, the illustration of FIG. 5 represents a snapshot of abrief moment right after the striker 120 contacts the striker plate 170.At this brief moment the housing 160 is isolated from the pins 178 ofthe strike plate 170. For example, as is shown in the alternate view183, the pins 178 are suspended within the slot 188 of the impactisolator 180 at this brief moment. This suspension allows the striker120 to transfer substantially all of its impact load directly on thestrike plate 170 with limited loss of energy being reflected back up thehousing 160. This is at least partially a function of the length of theslot 188 being located substantially in line with a line of impact ofthe striker 120. Further, not only does the impact isolator 180 allowthe impact load to be efficiently transferred to the strike plate 170,and thus surface 110, the reduced reflection allows the acceleratedweight drop to have a much longer effective lifespan.

By the time the pins 178 spring back up within the slot 188 in theimpact isolator 170 as a result of the static load being placed thereon,a majority of the impact load has already been efficiently transferredto the surface 110. Therefore, the reflection to the housing 160 isminimal. A reflection may exist up the striker 120, through the push rod130 and to the gas chamber 143. The cushioning means 168 are, therefore,placed proximate the gas chamber 143 and striker 120 to absorb thisreflected energy.

The accelerated weight drop constructed in accordance with theprinciples of the present invention provides many of the benefitsassociated with traditional seismic energy sources without providingtheir drawbacks. For instance, the accelerated weight drop constructedin accordance with the principles of the present invention is capable ofproviding a much greater impact load for its size, than could beprovided by the prior art accelerated weight drop systems. For thisreason, the accelerated weight drop constructed in accordance with theprinciples of the present invention may be manufactured much smallerthan the prior art devices, and therefore, is much easier to operate andmove from site to site. Additionally, the accelerated weight dropconstructed in accordance with the principles of the present inventiondoes not have the legal constraints associated with using the explosivesources, as well as does not have the placement constraints associatedwith the vibratory sources.

Turning briefly to FIG. 6, illustrated is a seismic survey system 600constructed in accordance with the principles of the present invention.The seismic survey system 600 illustrated in FIG. 6 initially includesan accelerated weight drop 620, which might be similar to theaccelerated weight drop 100 illustrated in FIG. 1, positioned over asurface 610 to create seismic waves therein.

Placed proximate the surface 610 for collecting information from theseismic waves created by the accelerated weight drop 620 is at least onegeophone 630. In the embodiment illustrated in FIG. 6, four geophones630 are being used. Those skilled in the art understand, however, thatany number of geophones 630 could be used and stay within the scope ofthe present invention. Wirelessly connected to the geophones 630 in theembodiment illustrated in FIG. 6 is a seismic recorder 640 configured torecord the collected information. I should be noted that the seismicrecorder 640 could just as easily been hardwired to the geophones 630.

Although the present invention has been described in detail, thoseskilled in the art should understand that they can make various changes,substitutions and alterations herein without departing from the spiritand scope of the invention in its broadest form.

1. An accelerated weight drop for use as a seismic energy source,comprising: a striker positionable over a surface; a compressed gasspring, said striker slidably coupled to said compressed gas spring,said compressed gas spring configured to drive said striker toward saidsurface thus creating seismic waves within said surface; and acushioning element positioned proximate said compressed gas spring andpositioned to dissipate reflected energy occurring through said strikerduring creation of said seismic waves.
 2. The accelerated weight drop asrecited in claim 1 wherein said compressed gas spring includes a gaschamber and a piston, wherein said piston is configured to slide withinsaid gas chamber to compress a gas therein to create a pressure thatdrives said striker toward said surface.
 3. The accelerated weight dropas recited in claim 2 further comprising a charging port coupled to saidgas chamber, said charging port configured to provide said gas withinsaid gas chamber.
 4. The accelerated weight drop as recited in claim 2wherein said compressed gas spring further includes a push rod and saidpush rod connects said piston to said striker.
 5. The accelerated weightdrop as recited in claim 4 wherein said cushioning element is locatedbetween said push rod and at least a portion of said striker.
 6. Theaccelerated weight drop as recited in claim 1 further including a strikeplate positionable between said striker and said surface wherein saidstriker is configured to strike said strike plate.
 7. The acceleratedweight drop as recited in claim 6 further including a housing at leastpartially surrounding said striker.
 8. The accelerated weight drop asrecited in claim 7 further including a catch mechanism coupled to saidhousing and configured to hold said striker in a cocked position.
 9. Theaccelerated weight drop as recited in claim 8 wherein said catchmechanism includes a trip dog coupled to said housing and configured tocooperatively engage said striker.
 10. The accelerated weight drop asrecited in claim 7 wherein said housing is coupled to a static load andis configured to transfer said static load to said strike plate.
 11. Theaccelerated weight drop as recited in claim 10 further comprising ahydraulic press coupled to said housing, said hydraulic press configuredto create said static load.
 12. The accelerated weight drop as recitedin claim 7 further including an impact isolator coupled to said housingand slidably coupled to said strike plate.
 13. The accelerated weightdrop as recited in claim 12 wherein said impact isolator comprises aplate having a slot formed therein, wherein a length of said slot ispositioned substantially in line with a line of impact of said striker.14. The accelerated weight drop as recited in claim 13 further includingan anvil having a pin therein coupled to said strike plate, wherein saidpin is slidably coupled within said slot.
 15. The accelerated weightdrop as recited in claim 7 wherein said housing has a main portion and asecondary portion, said main portion at least partially surrounding saidstriker and said secondary portion at least partially surrounding saidcompressed gas spring, wherein said cushioning element is locatedbetween said secondary portion and said compressed gas spring.
 16. Theaccelerated weight drop as recited in claim 1 further comprising ahydraulic lift coupled to said striker, said hydraulic lift configuredto lift said striker to a cocked position.
 17. A method for operating anaccelerated weight drop for use as a seismic energy source, comprising:positioning a striker over a surface, said striker slidably coupled to acompressed gas spring having a cushioning element positioned proximatethereto; and driving said striker toward said surface using saidcompressed gas spring to create seismic waves within said surface,wherein said cushioning element is positioned to dissipate reflectedenergy occurring through said striker during creation of said seismicwaves.
 18. The method as recited in claim 17 wherein said compressed gasspring includes a gas chamber and a piston, further including cockingsaid accelerated weight drop by sliding said piston within said gaschamber to reduce a volume of said gas chamber thereby pressurizing agas located therein, said pressurized gas used to drive said strikertoward said surface to create said seismic waves.
 19. The method asrecited in claim 18 wherein said compressed gas spring further includesa push rod and said push rod connects said piston to said striker, andfurther wherein a hydraulic lift is coupled to said striker to slidesaid piston within said gas chamber to reduce said volume of said gaschamber.
 20. The method as recited in claim 19 wherein said cushioningelement is located between said push rod and at least a portion of saidstriker.
 21. The method as recited in claim 19 wherein a catch mechanismholds said striker in a cocked position after sliding said piston withinsaid gas chamber to reduce said volume of said gas chamber.
 22. Themethod as recited in claim 21 wherein said catch mechanism includes atrip dog coupled to a housing of said accelerated weight drop andconfigured to cooperatively engage said striker.
 23. The method asrecited in claim 21 further including tripping said catch mechanismthereby causing said striker to drive toward said surface.
 24. Themethod as recited in claim 18 wherein a charging port is coupled to saidgas chamber, and further including charging said gas chamber using saidcharging port.
 25. The method as recited in claim 17 further including astrike plate positionable between said striker and said surface whereinsaid striker is configured to strike said strike plate.
 26. The methodas recited in claim 25 further including a housing at least partiallysurrounding said striker.
 27. The method as recited in claim 26 whereinsaid housing has a main portion and a secondary portion, said mainportion at least partially surrounding said striker and said secondaryportion at least partially surrounding said compressed gas spring,wherein said cushioning element is located between said secondaryportion and said compressed gas spring.
 28. The method as recited inclaim 26 further including coupling said housing to a static load,wherein said housing is configured to transfer said static load to saidstrike plate.
 29. The method as recited in claim 26 further including animpact isolator coupled to said housing and slidably coupled to saidstrike plate.
 30. The method as recited in claim 29 wherein said impactisolator comprises a plate having a slot formed therein, wherein alength of said slot is positioned substantially in line with a line ofimpact of said striker.
 31. The method as recited in claim 30 furtherincluding an anvil having a pin therein coupled to said strike plate,wherein said pin is slidably coupled within said slot.
 32. The method asrecited in claim 28 further comprising a hydraulic press coupled to saidhousing, said hydraulic press configured to create said static load. 33.A seismic survey system, comprising: an accelerated weight drop,including; a striker positionable over a surface; a compressed gasspring, said striker slidably coupled to said compressed gas spring,said compressed gas spring configured to drive said striker toward saidsurface thus creating seismic waves within said surface; and acushioning element positioned proximate said compressed gas spring andpositioned to dissipate reflected energy occurring through said strikerduring creation of said seismic waves; at least one geophone placedproximate said surface, said at least one geophone configured to collectinformation from said seismic waves; and a seismic recorder connected tosaid at least one geophone, said seismic recorder configured to recordsaid collected information.
 34. The seismic survey system as recited inclaim 33 wherein said compressed gas spring includes a gas chamber and apiston, wherein said piston is configured to slide within said gaschamber to compress a gas therein to create a pressure that drives saidstriker toward said surface.
 35. The seismic survey system as recited inclaim 33 further including a strike plate positionable between saidstriker and said surface wherein said striker is configured to strikesaid strike plate.
 36. The seismic survey system as recited in claim 35further including a housing at least partially surrounding said strikerand coupled to said compressed gas spring.
 37. The seismic survey systemas recited in claim 36 wherein said housing has a main portion and asecondary portion, said main portion at least partially surrounding saidstriker and said secondary portion at least partially surrounding saidcompressed gas spring, wherein said cushioning element is locatedbetween said secondary portion and said compressed gas spring.
 38. Theseismic survey system as recited in claim 36 further including a tripdog coupled to said housing and configured to hold said striker in acocked position.
 39. The seismic survey system as recited in claim 36wherein said housing is coupled to a static load and is configured totransfer said static load to said strike plate.
 40. The seismic surveysystem as recited in claim 39 further including an impact isolatorcoupled to said housing and slidably coupled to said strike plate. 41.The seismic survey system as recited in claim 40 wherein said impactisolator comprises a plate having a slot formed therein, wherein alength of said slot is positioned substantially in line with a line ofimpact of said striker.
 42. The seismic survey system as recited inclaim 41 further including an anvil having a pin therein coupled to saidstrike plate, wherein said pin is slidably coupled within said slot.